From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:59766) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1eFLqN-0003PT-S7 for qemu-devel@nongnu.org; Thu, 16 Nov 2017 10:12:44 -0500 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1eFLqI-0002O4-8l for qemu-devel@nongnu.org; Thu, 16 Nov 2017 10:12:43 -0500 Received: from mx1.redhat.com ([209.132.183.28]:33188) by eggs.gnu.org with esmtps (TLS1.0:DHE_RSA_AES_256_CBC_SHA1:32) (Exim 4.71) (envelope-from ) id 1eFLqI-0002Jk-3Q for qemu-devel@nongnu.org; Thu, 16 Nov 2017 10:12:38 -0500 Date: Thu, 16 Nov 2017 15:12:33 +0000 From: "Richard W.M. Jones" Message-ID: <20171116151233.GW2787@redhat.com> References: <20171115115246.GA1955@redhat.com> <20171116144746.GE29106@stefanha-x1.localdomain> <4ddf423b-a713-8f8b-e7dc-c970ad206885@kamp.de> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <4ddf423b-a713-8f8b-e7dc-c970ad206885@kamp.de> Subject: Re: [Qemu-devel] Effect of qemu-img convert -m and -W options List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Peter Lieven Cc: Stefan Hajnoczi , libguestfs@redhat.com, qemu-devel@nongnu.org On Thu, Nov 16, 2017 at 03:51:29PM +0100, Peter Lieven wrote: > Afaik all writes to the same QCOW2 serialize because of the s->lock that > is held during the write. So its not suprising that there is no benefit from > mutliple threads as long as reading from the RAW file involves no delay. > Which is likely due to readahead of the OS. I guess this would explain it, thanks. Rich. -- Richard Jones, Virtualization Group, Red Hat http://people.redhat.com/~rjones Read my programming and virtualization blog: http://rwmj.wordpress.com virt-df lists disk usage of guests without needing to install any software inside the virtual machine. Supports Linux and Windows. http://people.redhat.com/~rjones/virt-df/